Let $X$ be a Metric Space and let $\mathcal{B}$ be the Borel σ-algebra of $X$. Let $\Pi$ be a family of probability measures on $(X,\mathcal{B})$. Then, 1. If $\Pi$ is tight then it is relatively sequentially compact. 2. Suppose that $X$ is Separable and complete (i.e. Polish). If $\Pi$ is relatively sequentially compact, then $\Pi$ is tight.